A new method is proposed to characterize the molecular weight distribution (MWD) of polypropylene (PP). It is based upon the analysis of the curvature of the loss Tangent trace, Tanδ(ω), as obtained from a typical small amplitude oscillatory shear (SAOS) test. The result is a single number, MWD_(Tanδ) that correlates linearly with steady state recoverable shear compliance, J_e~0, as measured in a standard creep/recovery test and with M_z W_w issued from Gel Permeation Chromatography (GPC). In this respect, the Tand method is shown to outperform the well known relationship of Zeichner and Patel [1] for on-line process control of PP MWD.
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